DE102006043326A1 - Internal combustion engine e.g. diesel engine, controlling method for e.g. motor vehicle, involves varying temporal hydraulic distance between partial injections by proximate injecting process - Google Patents

Abstract

The method involves splitting a fuel metering into partial injections, and determining a temporal hydraulic distance between the partial injections. A value characterizing a pressure wave, which is produced by one of the partial injections, is detected. The temporal hydraulic distance between the partial injections is varied by a proximate injecting process such that the other partial injection is taken place at the preset value characterizing the pressure wave. Independent claims are also included for the following: (1) a device for controlling an internal combustion engine (2) a computer program comprising instructions to perform a method for controlling an internal combustion engine (3) a computer program product comprising instructions to perform a method for controlling an internal combustion engine.

Description

State of the art

The The invention relates to a method and a device for controlling an internal combustion engine according to the preamble of the independent claims.

object The present invention also relates to a computer program a computer program product for carrying out the method when the program runs on a computer or controller.

The increasing demands on direct-injection internal combustion engines, in particular diesel engines with regard to noise and pollutant emissions, require very high precision of the fuel quantity injected by the injection system over the entire service life and in all operating conditions of the internal combustion engine. By manufacturing tolerances, by wear / aging phenomena of the internal combustion engine or the injection system of the internal combustion engine and the mutual influence in the case of multiple injections, namely, pre-, main and post-injection, the actual injection quantities and injection timing of the applied setpoints can vary greatly. For example, disturbances are caused by pressure waves that are triggered by a first injection and that have not subsided during the time of the second injection in the injection system. In order to reduce these deviations, various correction methods are known from the prior art. So goes for example from the EP 1 303 693 B1 a method and a device for controlling an internal combustion engine, in which the pressure wave correction, the fuel injected at a second partial injection amount of fuel is corrected depending on a pressure variable, which characterizes the fuel pressure, the fuel quantity and another size. This further variable may be, for example, a variable characterizing the fuel temperature.

From the DE 103 28 789 A1 a method and a device for controlling an injection system comprising at least two injection elements of an internal combustion engine has become known in which a control signal which characterizes the fuel quantity to be injected by means of the at least two injection elements is corrected in dependence on a pressure wave influencing of the at least two partial injections in that a collective pressure wave correction is performed for the at least two injection elements and a collective correction function is determined, that individual characteristics of the at least two injection elements are detected and that the collective correction function is amplitude modulated by means of the detected individual characteristics of the at least two injection quantities.

These Pressure wave correction methods are used during the application phase applied, where correction functions are so bedatet that e.g. mutual interactions or disturbances are firmly compensated.

Furthermore are other methods, such as so-called zero-quantity calibration become known, which an adaptive change of Injektoransteuerwerte on the Life of the injector and in this way changes the injector behavior over consider its lifetime by adapting the injector drive values.

By These procedures will significantly reduce the injection tolerances reached. However, there are operating areas where there are significant variations of the injection system occur. These scatters can be through the described methods are not easily corrected. For example, the scatter is one immediately before a main injection pre-injection then very large, if before this pre-injection another pre-injection is applied. While doing so the amount of first pre-injection determined very precisely can increase, the tolerances increase in the second pilot injection because of the difficult-to-control pressure oscillations in the rail and in the injector supply lines. Since the pressure oscillations in the Supply line and in the rail of many factors can influence their influence on the injection quantity due to the pressure wave correction applied during the application are only insufficiently compensated, since not all influencing factors be taken into account can.

Problematic this is also that the known pressure wave correction no Control loop but only one control represents. During the Application takes place the Bedatung and in the production vehicle will later on basis the current operating point of the internal combustion engine, the correction value calculated without the actual to take into account adjacent rail pressure oscillation, that of others, not recorded influences and not considered known Operating conditions depends. This results in metering errors, which in turn lead to deterioration emissions and noise behavior to lead.

Disclosure of the invention

Advantages of the invention

The method according to the invention and the device with the features of the independent Claims, in contrast, instead of a controlled, inaccurate correction of the pressure oscillations, permits a correction on the basis of the actually measured pressure oscillations and thus a significantly better metering accuracy of, in particular, small quantities injected at times when pressure oscillations of an earlier injection still exist. For this purpose, during an injection process, at least one variable which characterizes a pressure wave triggered by the first partial injection is detected, and in a subsequent injection process the temporal hydraulic distance of the at least one second partial injection from the first partial injection is varied such that the second injection occurs at a predefinable one Pressure wave characterizing size takes place.

The basic idea The invention is the hydraulic temporal spray distance to determine. In known from the prior art method is however, only the electrical distance of two injections based for example, an injector signal measured.

Depending on Tolerances of the injector results from a hydraulic distance, which is unknown and has a significant influence on the quantity accuracy the subsequent injection has. Because of this hydraulic spray distance is unknown, is so far no online evaluation of the pressure curve e.g. possible in the rail or in the injector, as a safe detection of the beginning of the downstream injection from the superimposed Pressure waves from the first injection, for example, pre-injection, and second injection, for example, main injection, based on a individual pressure curve not possible is.

The basic idea Therefore, it is the hydraulic spray distance of the present invention between two adjacent partial injections, for example between a pilot injection and a main injection to determine and the temporal hydraulic distance of a second partial injection from the first split injection to vary so that the second Partial injection at a predefinable, defined, the pressure wave characterizing size takes place and so for example a compensation of pressure wave oscillations and thereby an improvement of the metering accuracy is achieved.

By those in the dependent Claims listed measures are advantageous developments and improvements of the independent claim specified device possible.

Of the hydraulic injection distance of the second partial injection and the first partial injection is advantageously carried out by an error injection to a the injection interval characterizing electrical drive signal with otherwise unchanged injection parameters performed.

These Fault connection preferably takes place in that the distance characterizing electrical drive signal at successive working cycles is varied by small values and from the comparison of Pressure oscillations in the injector of the start of injection and thus the hydraulic injection distance of the second partial injection of the first partial injection is determined. This provision is very exactly possible, since the rail pressure curves up to this time only by the first partial injection be determined and are the same in this respect. The spray distance is from the difference of the hydraulic injection start of the second Partial injection from the hydraulic injection start of the first partial injection, which is also easy to determine in this way.

So provides an advantageous embodiment, that detects a plurality of variables characterizing the pressure wave becomes. Preferably, the time course of the pressure wave is completely during the Operation of the internal combustion engine, i. recorded online.

Purely in principle, can be used to determine the time of the second injection Any size characterizing the pressure wave is used. Preferably, however, it is provided that as the pressure wave characterizing Size, at the second partial injection takes place, one or more of the following Sizes used are: time maximum, time minimum, a zero crossing of Pressure wave.

to suppression of disorders can they pressure curves and / or the calculated time intervals of the two injections over several Working cycles are determined and averaged.

The inventive method allows very advantageous to carry out a pressure wave correction independently from the arrangement of a pressure sensor in the injection system of the internal combustion engine. The detection of at least one, the pressure wave characterizing Size must In particular, do not use a pressure sensor on the injector. Possible It is also, this size using a in a pressure line and / or arranged in a rail pressure sensor to determine. By determining the time interval of the second Injection from the first injection to a predefinable one Pressure wave characterizing size is the Reproducibility even in a measurement example in the Given pressure line, as the pressure wave in the pressure line and / or essentially always the same in the rail.

Brief description of the drawings

embodiments The invention is illustrated in the drawings and in the following Description closer explained.

It demonstrate:

1 a schematic representation of a common rail system known in the prior art;

2 the variation of the injection scheme with a first pilot injection and a second pilot injection based on corresponding control signals of an injection system according to the present invention.

Embodiments of the invention

In the 1 For the understanding of the invention required components of a high-pressure fuel injection system are shown using the example of a common rail system. With 1 is a fuel tank called. The fuel tank is to promote fuel through a first filter 5 as well as a prefeed pump 10 with a second filter 15 in connection. From the second filter 15 From the fuel passes via a line to a high-pressure pump 25 , The connecting line between the second filter 15 and the high pressure pump 25 also has a low pressure limiting valve 45 having connecting line with the reservoir 1 in connection. The high pressure pump 25 stands with a rail 30 in connection. The rail 30 is also referred to as (high pressure) storage and in turn is on fuel lines with different injectors 31 in pressure-conductive connection. Via a pressure relief valve 35 is the rail 30 with the fuel tank 1 connectable. The pressure relief valve 35 is by means of a coil 36 controllable.

The pipes between the outlet of the high-pressure pump 25 and the inlet of the pressure relief valve 35 are referred to as "high pressure area." In this area, the fuel is under high pressure.The pressure in the high pressure range is measured by means of a sensor 40 detected. The pipes between the fuel tank 1 and the high pressure pump 25 are referred to as "low pressure area".

A controller 60 acts on the high pressure pump 25 with a drive signal AP, the injectors 31 each with a drive signal A and / or the pressure relief valve 35 with a drive signal AV. The control 60 processes different signals from different sensors 65 characterizing the operating state of the internal combustion engine and / or of the motor vehicle which is driven by this internal combustion engine. Such an operating state is, for example, the rotational speed N of the internal combustion engine.

That in the 1 shown injection system works as follows:

The fuel that is in the fuel tank 1 is, by means of the feed pump 10 through the first filter 5 and the second filter 15 conveyed. If the pressure in the low-pressure range increases in an unacceptably high manner, the low-pressure relief valve opens 45 and gives the connection between the output of the feed pump 10 and the reservoir 1 free.

The high pressure pump 25 promotes the amount of fuel Q1 from the low pressure area to the high pressure area. The high pressure pump 25 builds in the rail 30 a very high pressure. Usually, maximum pressure values of about 30 to 100 bar are achieved in injection systems for spark-ignited internal combustion engines and maximum pressure values of about 1000 to 2000 bar in the case of self-igniting internal combustion engines. By means of injectors 31 The fuel can thus be metered under high pressure to the individual combustion chambers (cylinders) of the internal combustion engine.

By means of the sensor 40 the pressure P in the rail or in the total high pressure range is detected. By means of the controllable high-pressure pump 25 and / or the pressure relief valve 35 the pressure is regulated in the high pressure area.

As pre-feed pump 10 Usually electric fuel pumps are used. For higher flow rates, which are particularly required for commercial vehicles, also several parallel feed pumps can be used.

In the 2 are typical Ansteuerverläufe for an injector in the case of two pilot injections VE1 and VE2 shown. The two signal waveforms represent different timing drive states in which the time interval between the two drive signals VE1, VE2 or VE1 * and VE2 * is varied in the manner described below.

In the following, the determination of the hydraulic distance t _{diff, hyd.} of the two injections VE1 and VE2 explained. In the case of processes known from the prior art, only an electrical signal t _{diff, electr.} Characterizing the time interval of the second partial injection VE2 from the first partial injection VE1 is determined _. measured by an injector signal. Depending on the tole the injectors results in a time interval of the actual injection, in the following short hydraulic distance t _{diff, hyd.} which is unknown and has a significant influence on the quantity accuracy of the subsequent injection VE2.

The basic idea of the invention is now to control the hydraulic spraying distance t _{diff, hyd.} to be determined and varied so that the second partial injection VE2 takes place at a predeterminable, the pressure wave characterizing size, or in other words to vary at a predetermined, the pressure wave characterizing size, which was triggered by the first partial injection VE1 , takes place. For this purpose, at least one variable which characterizes a pressure wave triggered by the first partial injection VE1 is also detected, as will be described below.

To identify the hydraulic distance between the first pilot injection VE1 and the second pilot injection VE2 while an error is applied to the injection interval characterizing (electrical) drive signal t _{diff, electr.} made with otherwise the same injection parameters. For this purpose, the distance characterizing (electrical) drive signal t _{diff, electr.} in successive steps by small values Δt _{diff, electr.} varied. From the comparison of the resulting pressure oscillations in the injector, the start of injection of the second pilot injection VE2 can be determined very accurately, since the rail pressure curves are determined up to this point in time only by the first pilot injection VE1 and are unchanged to that extent. From the difference with the likewise easily determinable start of injection of the first pilot injection VE1, the hydraulic distance t _{diff, hyd.} between the first pilot injection VE1 and the second pilot injection VE2 determine. It should be noted that the determination does not depend on the position of the pressure sensor 40 is dependent. Depending on the position of the pressure sensor 40 , For example, in the pressure line or rail, although different times, at which the hydraulic injection starts the first and second pilot injection can be detected. These depend on the velocity of propagation of the pressure waves between the injector and the sensor. However, since the propagation velocity is approximately equal to that for the second pilot injection VE2 for the pressure waves of the first pilot injection VE1, the hydraulic injection clearance may also be from the signal of the pressure sensors on the supply line to the rail to the injector or by means of the rail pressure sensor 40 be determined by yourself. A deterioration of the signal-to-noise ratio due to the damping of the pressure oscillations can be taken into account in a manner known per se.

According to the invention, not only the injection distance t _diff during application is determined, but also at least one characteristic characterizing the pressure wave at that time, eg the first minimum, the first zero crossing or the first maximum, etc. of the pressure wave. A signal characterizing this property is stored. Advantageously, the entire pressure curve over time, ie the characteristic of the pressure wave, is recorded and stored completely online. During operation in the production vehicle, the previously applied distance t _diff is then not set rigidly, but this distance is varied, that is to say the start of the second partial injection VE 2 is determined such that the second partial injection takes place at a predeterminable quantity characterizing the pressure wave. for example, at the first maximum or the first minimum. If this is not possible with the desired distance t _diff , then t _{diff is} adjusted correspondingly by a variation Δt _diff such that the applied position of the hydraulic injection start of the second partial injection VE2 is restored in relation to the phase position, that is to say the stored characteristic of the pressure oscillation. Accordingly, the second partial injection VE2 takes place at a given time with regard to the amplitude and phase position of the pressure wave and is thus reproducible in a very precise manner, whereby a high-precision pressure wave correction is likewise possible.

If the pressure oscillation is measured directly in the injector, the measured pressure values correspond to the values that determine the injection. By contrast, if the pressure oscillation is measured in the supply line or in the rail, by the arrangement of the sensor 40 in the high-pressure region, as in FIG 1 this is not the case. However, since the pressure waves caused by the first pilot injection VE1 and the second pilot injection VE2 are both equally changed by the "transmission system from the injector to the pressure sensor", features based on the relative evaluation between the two pressure waves remain as mentioned above Therefore, if the injection start of the second partial injection VE2 measured under application conditions in the rail at a certain characteristic of the pressure wave triggered by the first partial injection VE1 leads to the desired second partial injection VE2, then this characteristic of the pressure wave of the first pilot injection results even with changed ambient conditions VE1 adapted hydraulic injection start of the second pilot injection VE2 also to the desired injection quantity of the second pilot injection VE2th The method described above thus enables a high-precision determination of the by the pressure wave of the first pilot injection VE1 caused changes in the injected amount of the second partial injection VE2.

Claims (10)

Method for controlling an internal combustion engine, wherein the fuel metering is divided into a first partial injection (VE1) and at least one second partial injection (VE2), characterized in that the temporal hydraulic distance (t _{diff, hyd.} ) _Of the at least one second partial injection (VE2 ) is determined by the first partial injection (VE1) and at least one variable which characterizes a pressure wave triggered by the first partial injection (VE1) is detected and in a subsequent injection process the temporal hydraulic distance (t _{diff, hyd.} ) of the at least one second partial injection (VE2) of the first partial injection (VE1) is varied so that the second partial injection (VE2) takes place at a predeterminable, the pressure wave characterizing size. A method according to claim 1, characterized in that the temporal hydraulic distance (t _{diff, hyd.} ) _Is determined by fault injection to a the injection distance characterizing electrical drive _signal (t _{diff, elekt.} ) With otherwise unchanged injection _parameters . A method according to claim 2, characterized in that the fault connection takes place in that the electric drive _signal characterizing the distance (t _{diff, elekt .} ) Is varied by successive working steps by small values (Δt _{diff, electr.} ) And from the comparison of these resulting pressure _oscillations in the injector, the hydraulic distance (t _{diff, hyd.} ) Is determined. Method according to one of the preceding claims, characterized characterized in that a plurality of features which are characterized by characterize the first partial injection (VE1) triggered pressure wave, preferably the entire time course of the pressure wave detected becomes. Method according to one of the preceding claims, characterized characterized in that as the pressure wave characterizing size, at the second partial injection (VE2) takes place, one or more the following sizes are: a time maximum, a time minimum, a zero crossing the pressure wave. Method according to one of the preceding claims, characterized in that the at least one characterizing the pressure wave size by means of a arranged in a pressure line and / or in the rail pressure sensor ( 40 ) is determined. Device for controlling an internal combustion engine, wherein the fuel metering is divided into a first partial injection (VE1) and at least one second partial injection (VE2), characterized in that means are provided which show the hydraulic spraying distance (t _{diff, hyd.} ), And means , which detect a variable that characterizes a pressure wave triggered by the first partial injection (VE1), and in a subsequent injection process the time hydraulic distance (t _{diff, hyd.} ) of the at least one second partial injection (VE2) from the first partial injection (VE1 ) vary so that the second partial injection (VE2) takes place at a predeterminable magnitude characterizing the pressure wave. Apparatus according to claim 7, characterized in that the means for detecting the hydraulic spraying distance (t _{diff, hyd.} ), The means for detecting the pressure wave triggered by the first partial injection (VE1) and the means for varying the temporal hydraulic distance (t _{diff , hyd.} ) in a subsequent injection process by a control unit ( 60 ) of an internal combustion engine can be realized. Computer program that shows all the steps of a procedure according to one of the claims 1 to 6, which runs on a computing device. Computer program product with program code, which is stored on a machine-readable carrier, for carrying out the method according to one of claims 1 to 6, when the program is stored on a computer or in a control unit ( 60 ) is performed.